The present embodiments relate to correction of an x-ray image recorded with an x-ray device with an anti-scatter grid for effects of the anti-scatter grid.
In x-ray imaging, anti-scatter grids are already widely known in the prior art for reducing disruptive amounts of scattered radiation in the x-ray image obtained. Anti-scatter grids may be used, for example, in the area of angiography and radiography imaging. Known technical realizations mostly employ anti-scatter grids that use lead lamellas that may be manufactured especially thin for x-ray absorption. Although the lamellas have a very small strip width, the structures of the anti-scatter grid formed by the lamellas are to be taken into account accordingly during the calibration of the imaging x-ray device.
The simple geometrical structure and the thin strip width in known anti-scatter grids already enables an adequate image quality of the ultimate x-ray images to be insured by a conventional calibration, in which a calibration image of just the anti-scatter grid (e.g., without an imaging object) is to be recorded. The calibration image may later be subtracted from the actual x-ray image to remove the contributions of the anti-scatter grid and to obtain a corrected x-ray image. Then, the lamella structures of the anti-scatter grid are no longer recognizable in clinical x-ray images.
The restricted geometrical structure provides that the proportion of scattered radiation in the x-ray images recorded using a conventional anti-scatter grid continues to be quite high. The image quality may be very much adversely affected, which is shown, for example, in strongly-absorbing imaging objects (e.g., extremely obese patients).
Therefore, current approaches have been proposed, in which far more complex geometrical structures are used within anti-scatter grids to improve the absorption behavior. Absorption materials are also employed in such cases, which may be realized with higher strip widths. The complex geometries and, if necessary, greater strip widths make a calibration or the use of calibration images much more difficult, however.
Added to this effect is the fact that, with many x-ray devices (e.g., C-arm x-ray devices), the recording arrangement including the x-ray emitter and the x-ray detector may be put into different positions to be able to record the imaging object (e.g., a patient) from different projection directions. In such cases, mechanical effects (e.g., from gravity acting elsewhere) may come into play if different recording geometries are used when compared to the calibration image. While this would have a small influence with anti-scatter grids with more simple structures and/or extremely thin lead lamellas, with more complex geometrical structures and/or larger strip widths, a greater restriction of the image quality may arise. These types of changes to the recording geometries may also be the result of ageing effects of the x-ray device.